SUMMARY: Not so long ago, people argued that HBO wasn’t going to unbundle anytime soon, or ever. So what changed?

-- I got a lot of flack when I suggested in May that a network like AMC may be in a good position to unbundle from cable, and charge consumers for a Netflix-style service that would be available to anyone, even cord cutters. Many smart people said that it would never happen, and that any such move would drive cable networks out of business.

Fast forward five months, and it looks like the question isn’t so much if, but when: Over the last few days, cable networks and broadcasters have made a massive commitment to new online distribution models. First, HBOsaid that it will sell an online-only service in 2015. Then CBSfollowed by actually launching such a service the very next day. Just hours later, a Univision executive committed to talking the channel to cord cutters as well. And earlier this month, the NBAannounced that it reached a deal with ESPN to show live games outside of the cable pay gates.

The great unbundling has begun, and even close industry observers were taken by surprise. So why is everyone suddenly getting ready to unbundle? Here are three theories: